-Dh-
valence, easy oxidation and reduction, and a marked tendency
to form complexes.
and phosphorus,
the greatest
Except for the elements carbon, nitrogen,
the transition elements are concentrated to
degree by marine plants and animals over the
levels in the water (23,26).
These are the elements that form
the most stable complexes with organic chelating materials
(17,14,27) and it is most likely by this mechanism that the
heavy metals zinc,
copper,
nickel,
cobalt,
iron,
nese are concentrated in the marine biosphere.
and manga-
[ff surface
binding of these metals to organisms is a major factor for
their concentration then a concurrently important factor ts
that of the extent of the available organic adsorptive surface.
Plankton in the sea,
especially phytoplankton,
provide the
greatest surface area with respect to protoplasmic volume and,
in addition, probably provide a greater volume of living ma-
terial than any other of the marine organisms.
Thus, the major
initial concentration of radioactive zinc, cobalt, tron,
and
menganese from the environment probably occurs in the phytoplankton.
In addition to the surface adsorption of non-fissionproduct radioisotopes onto phytoplankton and zooplankton,
the
orocess of direct uptake and assimilation may well be of inmportance in these organisms.
The roles of these non-fission
elements in the phystology of planktonic organisms are not
known but in higher animal forms, at least, they are of major
importance.